The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Brush-Less Direct Current (BLDC) motors, also known as electronically commutated synchronous motors, use electronic commutation to control magnetic fields in a stator that cause movement of a rotor. Motor control circuits sense a rotational position of the rotor, herein referred to as the position of the rotor, to control timings of the electronic commutation.
In some BLDC motors, sensors such as of Hall-effect sensors are used to determine the position of the rotor. In contrast, sensorless BLDC motors may use Back-Electro-Motive Force (Back-EMF) detection to determine the position of the rotor while the rotor is moving.
When the rotor is in a stationary position, a technique called inductive sense may be used by sensorless BLDC motors in order to kick start the spinning. Inductive sense determines a position of a magnet according to differences in an inductance of a coil caused by a proximity and a polarity of the magnet relative to the coil. Because a rotor of a BLDC motor includes one or more magnets, a motor controller may determine a position of the rotor relative to one or more coils of the BLDC motor by measuring one or more inductances of the one or more coils.
At times, a BLDC motor may experience a rotor lock event, wherein the BLDC motor is not able to spin up. A rotor lock event may occur when the rotor becomes stuck in a single position. A rotor lock may also occur when the rotor cogs, that is, when the rotor oscillates such that the rotor repeatedly rotates forwards and then backwards between a first position and a second position without performing a full rotation.
If the motor controller continues to drive the BLDC motor during a rotor lock event, the BLDC motor will consume power unnecessarily and the coils of the BLDC motor will heat up. If the motor controller continues to drive the BLDC motor during a rotor lock event for an extended period, the heating of the coils may cause a catastrophic failure of the motor. In addition, when the motor is, for example, a fan motor, the system including the fan may also fail.
Therefore, a motor controller for a BLDC motor may include a capability to detect rotor lock events.